Due to its large surface area, mesoporous silica has received attention, rendering it useful for a variety of applications including as adsorbent in gas or liquid phase. Since the discovery of M41 S family mesoporous silicas, studies in ordered mesoporous materials have attracted extensive attention. SBA-15 mesoporous silica has been extensively studied due to its large pore size, thick pore walls, and high hydrothermal stability. These features are of great interest for various applications such as adsorption, catalysis, separations, and hard-templating synthesis of nanowires, nanotubes, ordered mesoporous carbons, polymers and metal oxides. Among the SBA type materials, SBA 16 is considered to be a particular interesting mesostructure, as it has a 3-D cubic arrangement of mesopores corresponding to the Im3m space group.
There are numerous reports on the synthesis, characterization, and applications of SBA-15 material. In general, the synthesis approaches to SBA-15 involve the self-assembly of block co-polymer at 40° C. for 24 h, followed by silica condensation at 100° C. or even higher temperature for 48 h under static condition (Kim, J. M., & Stucky, G. D., Chem. Commun. (2000) 1159). Somani et al. reported the synthesis of mesoporous silica under refluxing conditions. They concluded that the mesoporous silica prepared under refluxing condition showed better textural properties compared to that prepared by conventional static hydrothermal synthesis (Somani, R., et al., J. Porous Mater. (2005) 12, 87). Researchers also modified the synthesis by introducing cetyltrimethylammonium bromide (CTAB) as co-surfactant in order to control the textural, structural, and morphological properties of SBA-type mesoporous silicas. Ma et al. successfully obtained the mesoporous silica material with spherical morphology, further applied as the stationary phase in high performance liquid chromatography (HPLC) (Ma, Y., et al., Colloid Surf A (2003) 229, 1). Mesa et al. proposed that the presence of cationic CTAB could help to regularize the shape of micelles and their interaction with silica species, lead to a better mesostructure order of SBA-type materials (Mesa, M., et al., Solid State Sci. (2005) 7, 990).
Recently, several interesting results have been reported on the structural progress during the formation of hexagonal mesoporous silicas. Regev et al. presented an insight into the appearance of ordered cetyltrimethylammonium chloride (CTAC) micelle in a very short time (about 3 min) by cryogenic transmission electron microscopy (Cryo-TEM) and small angle X-ray scattering (SAXS) (Regev, O., Langmuir (1996) 12, 4940). Our results showed that the synthesis time of MCM-41 could be significantly reduced without affecting the quality in terms of mesostructural order (Liu, X., et al., Colloid Interface Sci. (2008) 319, 377). Considering the advantages of SBA-15 over MCM-41 silica, it would be highly desirable to have an effective and non-time-consuming recipe for the synthesis of highly ordered SBA-15. It is generally accepted that reducing the synthesis time can be the most applicable approach for large scale production of mesoporous materials in all synthesis methods.
Because the cage like SBA-16 mesostructured silica can only be produced in a narrow window of synthesis parameters (Zhao, D, et al., J. Am. Chem. Soc. (1998) 120, 6024), very limited SBA-16 synthesis methods have been reported so far. Using block co polymer F108 as template in presence of K2SO4 and HCl, SBA-16 single crystal (particle size ˜1 μm) was obtained under static condition by Yu et al. (Yu, C., et al., J. Am. Chem. Soc. (2002) 124, 4556; Yu, C., et al., Chem. Mater. (2004) 16, 889). Kleitz et al. (Langmuir (2006) 22, 440) reported the synthesis of SBA-16 silicas using F127-butanol H2O mixture at low HCl concentration. SBA-16 can be also prepared with CTAB being added as co-template (Lin, C.-L., et al., J. Phys. Chem. Solids (2008) 69, 415; Chen, B.-C., et al., Micropor. Mesopor. Mater. (2005) 81, 241); CTAB has been suggested to help control the morphology and regulate the shape of mesostructure. For instance, Mesa et al. (Solid State Sci. (2005) 7, 990) proposed that the presence of cationic CTAB can regulate the shape of micelles and their interaction with the silica precursors in the SBA-16 synthesis.
Accordingly it is an object of the present invention to provide a method of forming a particulate porous metal oxide or metalloid oxide that is fast and suitable for the formation of high quality mesoporous particles.